High current electric switch



1932. c. D. AINSWORTH HIGH CURRENT ELECTRIC SWITCH Filed May 31, 1930 2Sheets-Sheet Inoenior. M M LT Oct. 25, 1932. c AINSWORTH HIGH CURRENTELECTRIC SWITCH Filed May 31, 1930 2 Sheets-Sheet 2 Patented Oct. 25,1932 UNHTED STATES PATENT OFFICE CHESTER D. AINSWORTH, F WOLLASTON,MASSACHUSETTS, ASSIGNOR TO CONDIT ELECTRICAL MANUFACTURING CORPORATION,OF SOUTH BOSTON, MASSACHUSETTS,

A CORPORATION OF MASSACHUSETTS HIGH CURRENT ELECTRIC SWITCH Applicationfiled May 31, 1930. Serial No. 458,876.

This invention relates to electric switches and particularly to switcheswhich employ, in addition to the main current carrying contact members,auxiliary contact members hetween which the circuit interrupting are isdrawn. The usual down break electric switch consists of a pair ofupstanding conducting studs terminating at their lower ends in fixedcontact members which are adapted to be electrically connected by ahorizontal bridging member which is vertically movable into and out ofcontact engaging position. The magnetic flux in the vicinity of the U-shaped current path thus formed reacts on the movable bridging member tomove the contact members thereof, and particularly the resilientlymounted arcing contact members, downwardly out of engagement with theircooperating fixed contact members, thus to break the circuit and causearcing and burning at the contacts.

It is an object of this invention to provide a current conducting loopin the vicinity of nd including a movably supported contact member whichis so arranged that the magnetic forces set up by the current flowing inthe various parts of the loop react on the contact member and urge it ina switch closing direction into pressure engagement with its cooperatingfixed contact member.

It is a further object of the invention to provide a movable switchmember having a relatively long, generally horizontal contact memberwhich is pivotally supported at one l end, and a supporting structuretherefor ineluding a conducting member which is disposed in the samevertical plane and is generally parallel with said contact member, andthrough which he current traversing said contact member is arranged topass in a di rection to react magnetically on and urge said movablecontact member in a switch closing direction.

A further object of the invention is the provision of a movable switchmember having two superposed generally horizontal conducting members oneof which members compi..ses a movable contact member which is pivotallysupported at one end, whereby the nagnetic field set up by the currenttraversing the switch reacts on the movable contact member throughoutits length and at points remote from its pivotal support in a directionto urge said contact member upwardly in a switch closing direction.

A yet further object is to provide a movable switch member having agenerally vertically disposed U-shaped current path therethrough, onearm of the U-shaped path comprising a relatively long contact supportingarm having a pivotal support at one end and a contact member at its freeend.

A still further object is the provision of a movable switch memberhaving a movable contact member comprising a relatively long andhorizontal arm which is pivotally sup ported at one side of said switchmember and extends across and is provided with an arcing tip at theother side of said switch member, and conducting means disposed beneathsaid arm and in series therewith whereby to set up a magnetic field inthe vicinity of said arm when a heavy current traverses the switchcircuit which reacts on said arm throughout its length in a switchclosing direction.

A further object of the invention is the provision of a movable switchmember including a central vertical insulating rod and a movable contactarm which is pivotally supported atone side of said rod and extends in agenerally horizontal direction across and terminates at the other sideof said rod in a contact tip, and a rigid conducting support for saidarm which constitutes a current conducting path which is parallel withand reacts on said arm substantially throughout its length to urge it ina switch closing direction.-

In accordance with this invention, the contact or arcing members arecarried at the ends of long arms which are pivotally supported onopposite sides of the lifting rod. An object of the present invention isto provide conductors which will connect the pivoted end of said armsand at the same time be so arranged that they will react on the arms inthe proper direction to urge the arcing members upward.

A further object is generally to improve the construction andperformance of electric switches and contact structures therefor.

Fig. 1 is a side elevation of the contact structure embodying thepresent invention.

Fig. 2 is a sectional View taken along line 22 of Fig. 1.

Fig. 3 is a section along line 33 of F ig. 2.

Fig. 4 is a plan view of a clamping member.

Fig. 5 is a side elevation of the clamping member of Fig. 4.

Fig. 6 is a plan view of a connecter.

Fig. 7 is a diagrammatic perspective diagram of the current path throughthe movable switch member.

Fig. 8 is a sectional detail taken along line 88 of Fig. 2. I

The switch herein shown includes a pair of vertical conducting rods, orstuds, 10 which are supported in insulating bushings 12. Contactsupporting blocks 14 are fixed to the lower ends of said studs and areprovided with lower horizontal seats 16 on which the stationary contactmembers are detachably supported. Said stationary contact memberscomprise laminated brush members of the non-reactive or inverted type ofwhich one or more is adapted to be carried at the lower end of eachstud. The shank portions 18 of said brush members are enclosed bysheaths 20 and attaching bolts 22 are extended through the sheath andthe shank portion of the brush and are screw-threaded into said blocks14. Said brushes also include the downwardly and inwardly directed toeportions 24 which terminate in the generally horizontal contact faces26. In the switch here shown three parallel d brushes are associatedwith each conducting stud although the number of brushes may vary inaccordance with the current'capacity of the switch. Stationary contactor arcing members comprising iorizontally disposed cylinders or rolls 28are carried by each of said studs beneath the intermediate brush memberthereof. Said arcing members are supported between the depending spacedarms ofv a U-shaped frame 30 which is fixed beneath the middle brushmember by the attaching bolts 22 of the brush member.

The movable switch member includes a vertical insulating switch rod, orlifting rod, 32 and a transverse main current carrying bridging member34 which is provided with upper plane contact faces 36 which are adaptedto cooperate with the horizontal contact faces 26 of the several br ishmembers in the usual manner. The bridging member 34 is supported looselyat the lower end of the lifting rod 32 whereby to permit a degree ofpivotal movement thereof about its supporting rod. Said lifting rod isprovided with an annular shoulder 38 which defines the upper limit of adownwardly and outwardly flared end portion which is adapted to carrythe supporting means for tie main bridging member and also the auxiliarymovable arcing members hereinafter to be described. Said supportingmeans comprises a pairoi similar clamping members 39 and 40, Fig. 2, oneof which is shown most clearly in Figs. 4 and 5. Said clamping membersare identical and each has a vertical tapered recess 41 which recesscooperates to provide a pered passage that conforms with the flared orconical end portion 37 of the rod. Said clamping members are disposed onopposite sides of the switch rod and areheld fixedly in place on saidconical end portion by means of apair of clamping bolts 42 one of whichis disposed on either side of the switch rod and which are insulatedfrom the clamping members by means of insulating bushings and washers 44and 46. Said clamping memberswhen in position on said rodare adapt ed tobe spaced apart at their inner confronting faces whereby to provide agap 48 therebetween. It will thus be evident that the two complementalclamping members are insulated from each other by the rod 32. Each ofsaid clamping members is provided with an outstanding bracket 50 whichterminates in an upstanding arm 52, which arms are dis posed in avertical plane including the insulating switch rod 32, and are receivedlooselybetwe-en pairs of parallel depending flanges 54 of said bridgingmember, see especially Fig. 8. Pivot pins 55 extend transversely throughsaid flanges 54 and the ends of said arms 52 whereby to support thebridging member for pivotal movement about said pins as an axis. Meansare provided to 1nsulate said bridging member and the pivot pins 55 fromthe upstanding arms 52 of, the clamping members. To this end acylindrical insulating bushing 56 surrounds each of the pins 55 in theflanges 54 and insulating washers 57 are carried by said bushing andinterposed between the opposite faces of said arms 52 and the dependingflanges 54 of the bridging member. The above arrangement prevents theconducting bridging member from establishing electrical connectionbetween the insulated clampingmembers which it is supported. Thebridging member is provided with pairs of spaced vertical ribs 58 atopposite edges which are disposed on opposite sides of the pivot pins 55which project somewhat beyond said bridglng member. Cotter pins 60extend through said ribs and said pins 55 and the insulating bushings 56therefor thus to prevent axial displacement of the pins and thebushings.

Each of said clamping members has a horizontal outstanding bracket 62which is provided with an angularly related section 64. As shown mostclearly in Fig. 2 when the clamping members are secured in position onthe switch rod 32 the sections 64 of said arms are extended in oppositedirections and terminate in upstanding bracket 66 which are disposed inline with the switch rod but occupy diagonally opposite positionsrelative to the bridging member 34. Said outstandmg arms'62 are ofgoodconducting material such as bronze or low resistance composition andare provided with integral depending ribs'68'thus to provide increasedrigidityand strength. Said brackets 66 are provided with upstandingbosses 70 which engage the U- shaped insulating members 72 which aresecured to peripheral depending ribs 7 4 on the bottom face of thebridging member 34:. hen the bridging member is in :a horizontalposition, the insulating members 72 are adapted to be somewhat above thebosses 70 thus to permit a limited pivotal movement of the bridgingmember about the pivotal supporting pins 54:.

Each of said brackets 66 constitutes the support for a relatively longand generally horizontal contact supporting arm 76. Said arms aresimilar and are provided at one end with spaced parallel bifurcations 78which receive closely thcrebetween the upper end of a separa esupporting bracket 66. A pivot pin 80 extends through said bracket andthrough and beyond said bifurcations and is held in position by means ofcotter pins at either end thereof. Said arms 76 are inwardly refiexed ata point intermediate their ends whereby to provide sections 82 adjacenttheir free ends which overlie and are parallel with the clamping membersand particularly the sections 63 of said clamping members. Said arms 76are provided with vertical seats 84: at their free ends and arcingmembers comprising horizontal cylinders or rolls 86 are secured edlythereto by bolts 88. Said arcing members, by reason of the bends in saidarms 7 6 are centrally located in a common vertical plane with theswitch operating rod 32.

Each of said clamping members is formed with a vertical slot therein atthe side opposite the extended bracket 62 to provide a seat 90 for thelower end of upstanding conducting bars 92 and 93 associated withclamping members 39 and .0, respectively, which are secured fixedlythereto in good conducting relation by bolts 94. The bars 92 and 93 ofsaid clamping members are electrically connected at their upper endsbymeans of a generally circular connector 96, Fig. 6, which is providedwith a central passage 98 therethrough in which the switch rod 32 isfreely located. Said connector has bosses 100 which are formed withvertical seats 102 to receive the upper ends of said bars 92 and 93.Bolts 10% serve to connect the upper ends of said bars mechanically andelectrically to the connector.

Each of said contact supporting arms 7 6 is elect "ically connected withits supporting bracket 66 by means of a flexible conducting braid 106which is electrically connected at its opposite ends to said contactmember and bracket by means of attaching screws 108 and 169. Said arms76 are adapted normally to be biased for movement in an upward directionabout their pivotal supports whereby to urge the "movable arcing members86 into engagement with the cooperating fixed arcing members 28. To thisend a compression spring is provided on the extended ends of each pivotpin 80 and has an intermediate de pending portion 110 which bearsagainst the inner vertical face of said brackets 66 and angularlyrelated end portions 112 which are I Said stop members are insulatedfrom their supporting clamping members by suitable means as the sheetinsulation 118 and insulating washers 120 which are disposed beneath andaround the attaching bolts 116. At their upper ends said stop membersare provided with angularly related ears 122 which overlie said arms 76and against which said arms are adapted to abut in the switch openposition thereof. The stop members 114: also constitute verticalabutments against which the inner faces of said contact supporting armsrest and which resist the magnetic forces tending to attract theparallel arms due to the currents flowing therein.

In Fig. 7 the current path through the movable switch member has beendiagram= matically illustrated. Assume at a given in stant that thecurrent is passing through the switch from the left hand to the righthand arcing member 86 as indicated by the arrows in Fig. 7. It will beobvious that current flowing in each contact arm 7 6 and that flowing inthe current path of the clamping member th-erebeneath is in oppositedirections. Due to the close relation of these parallel currentconducting paths a strong magnetic reaction is set up which tends torepel the contact arms 76 in an upward direction. From an inspection ofFig. 2 it will be evident that by the disposition of the conducting bars92 and 93 of the clamping member closely adjacent the bracket 66 of theopposite clamping member that the current flowing through the clampingmembers must traverse a path parallel with the contact arms 76 whichextends substantially along the entire length thereof.

Due to the length of the pivoted contact arm 76, the reaction of thecurrent flowing in the section 63 of the clamping member, which isdirectly beneath the contact member and is disposed at a considerabledistance from its pivot pin, results in a relatively strong force. Bythe arrangement of the long contact arms 76 which are pivoted onopposite sides of the switch member from which their arcing members arelocated, it is possible to obtain sufli- Ill) its

cient reaction due to the localized magnetic loop including the contactmember to successfully oppose the opposite reaction of the currentflowing through the generally U- shaped current path of the switch andto pro vide an excess reaction which forces the stationary movablearcing members firmly together. At the same time the arrangement permitsa closer spacing of the stationary switch members with the long contactsupporting arms.

The angularly related portions of the current path between the movablearcing members also set up a magnetic field which is present in the arezone between the separable arcing members and reacts strongly on thecircuit interrupting arcs to blow them outwardly and into intimatecontact with the cool oil in which the switch is immersed, whereby toeffect the rapid extinguishment oi the arcs.

The magnetic field isthe resultant of several components. The magneticfield set up by the arms 76 and 62 has a horizontal axis and tends toforce the arc radially outward. The field set up by the loop composed ofthe conducting arms of the two clamping members acts in a verticaldirection. The two fields react to produce a component that acts toforce the arc outward and. at the same time laterally. This direction ofthe blow-out effeet is advantageous since, because the switch componentsare usually contained in a cylindrical oil receptacle, the arc musttravel over a longer distance beioreit engages the receptacle wall orthe insulating liner thereof than if it were blown radially outward. Theare blow-out path is thus more or less tangential to the inner surfaceof the receptacle so that the arcs are deflected into large masses ofoil, the dielectric strength of which is not critical to insulation ofthe switch, and have a long path of movement and a good chance ofbecoming cool and de-ionized and the gases dissipated before they comein contact with some conducting part of the switch. The direction ofdeflection of both arcs is in the same sense about the vertical axis ofthe switch so that the possibility of intermingling of the conductinggases and theresulting establishment of a single uncontrollable arebetween the stationary switch member is reduced to a minimum. Eachmovable arcing member 86 is connected to an arm 7 6 only at one end, theother end being free, so that the arc can be deflected in the directionof the free end without coming in contact with-a conducting part of thecircuit through the arcing members.

Various changes may be made in the construction and arrangement of theparts without departing from the scope of the invention.

I claim:

1. A movable switch member for an electric switch including a verticallifting rod,

a rigid conducting support secured to the loW- er end of said rod andextended on opposite sides thereof, and a generally horizontal movablecontact arm having a pivotal support at I on opposite sides thereof, ahorizontal arm having a pivotal support at one end thereof on saidsupport at one side of said rod and having a contact member at its freeend which is disposed on the opposite side of said rod, and means todirect current to flow in opposite directions in said arm and support.

8. A. movable switch member for an electric switch including a verticalinsulating rod, a rigid conducting support to the lower end of said rodhaving a conducting section which extends transversely of said rod onopposite sides thereof, a movable contact member comprising a generallyhor zontal arm having a pivotal support at one end on said support whichis located at one side of said rod and having a contact tip at its freeend which is disposed on the opposite side of said rod, said arm and theconducting section of said support being in the same vertical plane, andmeans to direct current to flow through said arm and said support in adirection to bias said movable contact member in a switch closingdirection by reason of the magnetic reaction of the current flowingtherein.

l. A movable switch member for an electric switch including a verticallifting rod, 21 contactstructure carried at the lower end of said rodcomprising a pair of complemental clamping members fixed to said rod,said clamping members being insulated from each other, contact memberseach having a pivotal connection one end with a separate one of saidclamping members, and means to direct current to flow in parallel pathsthrough said contact members and clamping members whereby to reactmagnetically on said con tact members to urge them in a switch closingdirection.

5. A movable switch member for an electric switch including a verticallifting rod, a transverse bridging member pivotally supported at thelower end oi said rod, a rigid conducting support secured to the lowerend of said rod beneath said bridging member having a horizontalconducting section which extends transversely on opposite sides of saidvertical rod, a conducting arm overlying said conducting s ction havinga pivotal connection with said support on one side of said rod andhaving a contact member disposed at its free end and on the oppositeside of said rod.

6. A movable switch member for an electric switch including an axiallifting rod, a transverse bridging member carried by the lower end ofsaid rod, a rigid conducting support car d by the lower end of said rodbeneath sa o l ridging member having a horizontal conducting sectionwhich extends on opposite sides of the axis of said rod, a generallyhorizontal arm disposed above and parallel with said conducting sectionwhich is pivotally connected with said support at one side of saidswitch rod and which car ries a contact member at its other and free endat the opposite side of said switch rod.

7. A movable switch member for an electric switch including a centraland vertical lifting rod, a movable contact member comprising an armwhich is pivotally supported at one side of said rod and extends in agenerally horizontal direction across and terminates on the other sideof said rod in a contact member, and a rigid conducting support for saidarm which constitutes a current conducting path which is parallel withand which reacts on said arm to urge it in a switch closing direction.

8. A movable switch member for an electric switch including a verticallifting rod, a rigid conducting support carried by the lower end of saidrod having a horizontal conducting section which extends transverse- 1yon opposite sides of said rod, a movable contact arm comprising agenerally horizontal arm which is disposed above and is generallyparallel with said conducting sectionhaving a pivotal support at one endthereof on said support at one end of said section, and having a contactmember at its free end which is disposed on the opposite side of saidrod adjacent the other end of said conducting section, means normallybiasing said contact member for upward movemcnt about its pivotalsupport, and means electrically connecting said contact member andsupport arranged to direct current to flow therethrough in a directionto assist said biasing means by the magnetic forces set up by thecurrent flowing therein.

9. A movable switch member for an electric switch including a verticallifting rod, a rigid supporting member fixed to the lower end of saidrod including a horizontal conducting section which extends transverselyof said rod and on opposite sides thereof, a bridging member pivotallymounted on said support and having a central aperture through which saidrod extends, an auxiliary contact member comprising a generallyhorizontal arm which is pivotally mounted on said support at one end andwhich carries a contact member at its free end, said arm having itssupport located at one side of said lifting rod and having its contactmember located at the opposite side thereof, said arm being above and inthe same vertical plane with the conducting section of said support,resilient means normally biasing said arm in a switch closing direction,and means electrically connecting said arm with said supportin g memberarranged to direct current to flow in parallel paths through saidclamping member and said arm whereby to exert a re active effect on saidarm substantially throughout the entire length thereof.

10. A movable switch member for an electric switch including a verticallifting rod, a rigid conducting support carried by the lower end of saidrod comprising a pair of insulated clamping members adapted to receivethe end. portion of said rod, said clamping members having oppositelyand outwardly extended horizontal brackets which are disposed onopposite sides of said rod and which terminate in upstanding bosses,each of said clamping members and the brackets thereof constituting ahorizontal current conducting path, a pair of movable contact memberscomprising generally horizontal arms which are pivoted at one end to theterminal bosses of said brackets and which extend on opposite sides ofsaid rod above the horizontal currentconducting paths comprising aclampingmember and bracket, arcing members carried by the free ends ofsaid arms, and electrically conducting means connecting said clampingmembers arranged to direct the current in said arms to flow in thehorizontal path through said clamping members and brackets in adirection to urge said arms throughout the length thereof in the switchclosing direction by reason of the repulsive effect of the magneticfield 'in the vicinity of said arms.

11. A movable switch member for an electric switch including a centraland vertical lifting rod, a rigidconducting support fixed to the lowerend ofsaid rod comprising a pair of clamping members having centralupstanding arms, a transverse bridging member pivotally supported onsaid arms and having a central aperture through which said rod extends,said clamping members having horizontally extended brackets whichproject on opposite sides of said rod and which terminate in upstandingbosses that are located beneathsaid bridging member at diagonallyopposite corners thereof, said clamping members and the brackets thereofconstituting horizontal current conducting paths, movable contactmembers comprising generally horizontal arms pivoted at one end to thebosses of said brackets and having contacts at their free ends andextended in opposite directions and on opposite sides of said switch rodin general parallel relation'and in the same vertical plane with thecurrent path through said clamping members and the brackets thereof, andmeans electrically connecting -which terminate in upstanding bosses thatare located beneath said bridging member at diagonally opposite cornersthereof, said clamping members and the brackets thereof constitutinghorizontal current conducting paths, vertical conducting bars fixed toand upstanding above the opposite ends of said clamping members, meanselectrically connecting said bars whereby to connect the horizontalcurrent paths electrically in series, and movable contact memberscomprising generally horizontal arms having arcing members at their freeends and having a pivotal support at their opposite ends on therespective bosses of said brackets, said arms arranged to overlie thecurrent conducting paths including said clamping members and thebrackets thereof.

13. A movable switch member for an electric switch including a centraland vertical lifting rod, a rigid conducting support fixed to the lowerend of said rod comprising a pair of clamping members having centralupstanding arms, a transverse bridging member pivotally supported onsaid arms and having a central aperture through which said rod extends,said clamping members having horizontally extended brackets whichproject on opposite sides of said rod and which terminate in upstandingbosses that arelocated beneath said bridging member at diagonallyopposite corners thereof, said clamping members and the brackets thereofconstituting horizontal current conducting paths, movable contactmembers comprising generally horizontal arms pivoted at one end to thebosses of said brackets and extended in opposite directions and onopposite sides of said switch rod in general parallel relation and inthe same vertical plane with the current path through said clampingmembers and the brackets there-of, said arms having contacts at theirfree ends, means electrically connecting the diagonally opposite ends ofsaid clamping members which lie adjacent the pi voted ends of said arms,and means carried by and insulated from said clamping members havingvertical attaching portions and hav ing horizontal port-ions whichoverlie said arms whereby to support sald arms against undue lateralmovement due to the attractive 14. In an electric switch the combinationof a pair of spaced vertical switch members terminating in contactmembers at their lower ends, a movable switch member includin avertically reciprocable insulating rod which is disposed between and inthe same vertical plane said switch members, a rigid con ducting supportcarried by the lower end of said rod having outstanding brackets whichconstitute with said clamping members parallel current conducting pathson opposite sides of said switch rod, bosses formed integral with theends of said brackets, generally horizontal arms having a pivotalsupport at one end on said bosses and arranged to overlie the parallelcurrent conducting paths of said support, contacts carried by the freeends of said arms, and means to direct current to flow through said armsand the current paths of said support in a direction to urge said armsthroughout their length by reason of the magnetic reaction in adirection to engage said fixed contact members.

15. An electric switch comprising stationary switch members and acooperating movable switch member having a lifting rod, a pair ofcurrent conducting contact arms located on opposite sides of said rod,each armhaving a pivoted connection with said rod under a separate oneof said stationary switch members and having at its free end a contactmember which co-operates with said other stationary switch member, andan electric connection between said pivotally connected ends of saidarms which provides conducting parts located adjacent said arms andtraversed by current which reacts on said arms in a direction to urgethem against said stationary switch members. 7

16. An electric switch comprising stationary switch members and acooperating movable switch member having a lifting rod, a pair ofcurrent conducting contact arms located on oppositesides of said rod,each arm having a pivoted connection with said rod under a separate oneof said stationary switch members and having at its free end a contactiember which cooperates with said other stationary switch member, and anelectric connection between said pivotally connected ends of said armswhich provides conducting parts located under and parallel with saidarms and traversed by current in theopposite direction to the currenttraversing said arms, whereby to react on said arms and to urge them forupward movement about their pivotal con nections.

17. A movable switch member for an electric switch comprising stationaryswitch.

members, a movable switch member having a vertical lifting rod, a pairof parallel current carrying contact arms disposed on opposite 1r. ad

sides of said rod and having pivotal connections therewith on oppositesides of said rod, contact members carried by the free ends of saidarms, and an electric connection between the pivotally connected ends ofsaid arms which provides conducting parts located in parallel proximitywith said arms and traversed by current in a direction to reactmagnetically with the current traversing said arms and to urge said armsagainst said stationary switch members.

18. An electric switch having stationary switch members and a movableswitch member including spaced pivotally supported arms having contactmembers at their free ends which cooperate with said stationary switchmembers, and a conductor electrically connecting the pivotally supportedends of said arms having sections which provide vertical loops ith saidarms and a horizontal loop between said arms.

19. [in electric switch having stationary switch members and movableswitch member including spaced pivotally supported arms having contactmembers at their free ends which cooperate with said stationary switchmembers, and a conductor electrically connecting the pivotally supportedends of said arms having sections which provide vertical loops with saidarms and a horizontal loop aetween said arms, and a lifting rod whichsupports said arms and conductor eX- tended through said horizontalloop.

20. An electric switch having stationary switch members, a movableswitch member comprising a lifting rod, a contact support on the lowerend of said rod including two clamping members between which said rod isengaged, means insulating said clamping members from each other, andcontact mem bers connected each with a separate one of said clampingmembers.

21. ran electric switch having stationary switch members, a movableswitch member comprising a lifting rod, a contact support on the lowerend of said rod including two clamping members between which said rod isengaged, means insulating said clamping members from each other, abridging member connected with and insulated from both of said clampingmembers, and contact members connected each with a separate one of saidclamping members.

22. An electric switch having stationary switch members, a movableswitch member comprising a lifting rod, a contact support on the lowerend of said rod including two clamping members between which said rod isengaged, means insulating said clamping members from each other, abridging member connected with and insulated from both of said clampingmembers, means electrically connecting said clamping members whichencircle said lifting rod, and contact members connected each with aseparate one of said clamping members.

23. An electric switch having stationary switch members, a movableswitch member comprising a lifting rod, a contact support on the lowerend of said rod including two clamping members between which said rod isengaged, means insulating said clamping members from each other, andcontact members each pivotally connected with a separate one of saidclamping members and overlying a conducting part of the other clampingmember, and means electrically connecting said clamping members.

24-. An electric switch having stationary switch members, a movableswitch member including pivotally supported parallel arms having arcingmembers at their free ends which cooperate with said switch members,means electrically connecting the pivoted ends of said arms so that theyare traversed by current in the same direction, and insulated meanswhich engages said arms and holds them against movement toward eachother due to attractive effect of the parallel currents.

In testimony whereof, I have signed my name to this specification.

CHESTER D. AINSWORTH.

